One of the most pervasive extended care patient assisting devices found within most modern hospitals is that known generally as respirators. The general function of such respirators is to aid the breathing function of respiratorily impaired patients while healing and medical treatment proceeds. Such respirators are often utilized in combination with trachea insertion devices as well as oral inhalers. In most respirators, a delivery tube and a return tube couple the respirator to the patient. To aid in treatment and the administering of vaporizable liquid such as medicines or the like, respirators are often provided with a device known generally as a medical nebulizer or simply nebulizer. The basic function of the nebulizer is to vaporize or atomize a liquid and transfer the vaporized or atomized liquid to the airstream on its way to the patient. While a great variety of nebulizer designs have been provided, most generally include a housing having an airflow passage passing therethrough and a reservoir for receiving and holding the to-be-vaporized liquid. A vaporizing chamber is maintained in communication with the airflow passage and means are provided for drawing the liquid into the vaporizing chamber.
Medical nebulizers are subject to several problems some of which are common to nebulizers generally. Perhaps one of the most critical problems or limitations arises in the position sensitivity of most nebulizers. On the one hand, it is desirable in many instances to position the nebulizer relatively close to the patient while on the other hand, the tendency of patients to move about leads to a contrary desire to support the nebulizer some distance from the patient and use an extended delivery tube. When extended delivery tubes are utilized, the possibility of the vaporized liquid condensing within the delivery tube becomes greater which severely limits the effectiveness of the nebulizer and may deprive the patient of the intended dosage of liquid. In addition, the transfer of liquid into the patient's respiratory system is extremely undesirable and may cause harm or discomfort to the patient.
In addition to problems associated with position sensitivity and condensation with the delivery tube, an overall problem or limitation to which nebulizers used in medical apparatus are particularly sensitive is the resistance imposed upon the respiratory airflow by the nebulizer. Many prior art devices provide effective vaporization at the expense of excessive air resistance and have been found on balance to be less than desirable in practical use.
To meet these problems and limitations, practitioners in the art have provided a variety of improved devices both within the medical arts and other related arts. For example, U.S. Pat. No. 5,008,048 issued to Ryder, the applicant of the present application, sets forth a POSITION INSENSITIVE ASPIRATOR which includes a hollow housing communicating with a source of carrier gas and a source of gas under pressure. A nozzle is disposed within the hollow housing through which the pressurized gas is directed to produce a high speed stream of gas. An entrainment member defining an aspiration chamber for the liquid is disposed in the housing with the aspiration chamber immediately adjacent to the nozzle outlet in the housing. A multi-directional liquid flow path is defined by the entrainment member edge portions to provide fluid communication regardless of the orientation of the device.
U.S. Pat. No. 4,743,407 issued to Apel, et al. sets forth a EXTERNALLY PRESSURIZED POROUS CYLINDER FOR MULTIPLE SURFACE AEROSOL GENERATION AND METHOD OF GENERATION in which a nebulizer includes a cylindrical gas permeable active surface. A sleeve is disposed around the cylinder and gas is provided from the sleeve to the interior of the cylinder formed by the active surface. In operation, a liquid is provided to the inside of the gas permeable surface which is wetted with the to-be-vaporized liquid.
U.S. Pat. No. 4,993,436 issued to Bloom, Jr. sets forth an ASPIRATING AND VOLUTIZING LIQUID DISPENSER in which a container and a mouthpiece are adapted to deliver a volutizable liquid orally to the user. A volutizing chamber is defined between the liquid reservoir and the container and the drawing passage in the mouthpiece through which the user inhales. A permeable fluid barrier separates the liquid in the reservoir from the open pore material which fills the volutizing chamber and limits the amount of liquid which can be aspirated through the open pore material to the user.
U.S. Pat. No. 4,512,341 issued to Lester sets forth a NEBULIZER WITH CAPILLARY FEED in which the feed to the spray nozzle is through a narrow space between the flat bottom of the liquid reservoir and a flange fixed to the bottom of the spray nozzle, where the space is narrow enough to draw liquid toward the spray nozzle by capillary action and aspiration at any orientation of the nebulizer between vertical and horizontal.
While the foregoing described devices representative of the prior art have, in some instances, provided improved nebulizer performance and capability, there remains nonetheless a continuing need in the art for ever more improved and effective nebulizing devices.